There are many types of towed vehicles, such as trailers and the like, which are not visible in one or more rear view mirrors mounted on the towing vehicle. The problem is particularly acute with wide recreation vehicles or motor homes. Since a narrow vehicle being towed behind a motor home is not visible to the driver of the motor home in the sight lines of any of his side mounted rear view mirrors, or the centre mounted rear view mirror, if applicable, the driver has no idea whether the vehicle is behaving properly.
There are many things which can go wrong with a towed vehicle. The hitch can fail or come loose. One of the tires can become flat. A wheel bearing can seize. An axle can bend or fail. Some part of the suspension can fail. The towed vehicle can be struck from the rear. Since the motor home or towing vehicle is heavy and has a lot of momentum, it is very difficult for the driver of the towing vehicle to sense through the feel in the steering wheel that something is wrong with the towed vehicle, particularly if it cannot be seen.
In the absence of a timely warning to the driver of the towing vehicle, hitch failure may result in the loss of the towed vehicle or the development of various hazardous conditions. Without the generation of an early warning to the driver when tire, bearing, axle, or suspension problems begin to develop, the driver of the towing vehicle will carry on until a serious problem has occurred such as having the trailer dragged behind the towing vehicle thereby resulting in damage or destruction of the towed vehicle. The heat generated by dragging a trailer over a prolonged distance, with a low or flat tire or with metal in contact with pavement, presents a danger of fire to inflammable components which may then consume the towed vehicle when the towing vehicle is eventually stopped. Minor rear end impact is difficult to detect, yet it can be sufficient to damage a towed vehicle without alerting the driver of the tow vehicle.
When the towed vehicle is or is not visible to the driver of the towing vehicle, it is still a problem with long towed vehicles such as trailers to determine in the rear view mirror the precise position of the rear end of the trailer. When the markers are mounted at the extreme side rear of the towed vehicle, the markers identify the rear point, giving the driver increased judgement for safer lane changes, maneuvering through tight spots, parking and backing up. For example, with a boat behind a motor home, it is difficult for the driver to back the boat or boat trailer to the water without jack-knifing. The markers mounted on each side of the boat trailer duplicate the movement or location of the boat and assist in backing up.
The foregoing problems have recently been addressed by "high tech" solutions, such as mounting a video camera on the back of the towing vehicle with the camera focused upon the towed vehicle. The video camera solution is expensive and does not provide a complete solution because it does not give an early warning of developing problems. The camera is unavoidably mounted on the top of the towing vehicle and is focused on the top of the towed vehicle. If the video camera is mounted on either side, it is vulnerable to damage by vandalism or colliding with a stationary object. A problem manifesting itself in a change in the positioning of the towed vehicle must be well advanced in order for the problem to be visible in the video camera from that vantage point.
U.S Pat. No. 4,257,706, Smith, issued Mar. 24, 1981, discloses motor vehicle back-up limit gauging methods and apparatus which include a pair of line-of-sight indicators affixed to the left side of the vehicle. They are placed in such positions that the driver of the vehicle when seated in the driving position may establish a line-of-sight by aligning these indicators through the existing rear view mirror. He or she may then back the vehicle to a safe distance from a building wall or other marker by halting the backward progress of the vehicle when the aligned indicators coincide with the ground line of the wall, or with the marker. There is no teaching of a marker and monitor system which relates the position or condition of the towing vehicle with the towed vehicle.
The invention disclosed in U.S. Pat. No. 2,984,011, Hamilton, issued May 16, 1961, relates to a towed vehicle hitching guide which may be used in conjunction with a rear view mirror on the driver's side of the vehicle to enable the driver to properly steer the towing vehicle while backing it up to line up the hitching connection on the towing vehicle with the corresponding connection on the towed vehicle. This system does not enable the driver to monitor the position or condition of the trailer.